Sebastian Vettel has failed to complete three of the nine races and is without a victory so far this season

Red Bull's Sebastian Vettel says Formula 1 can be a "very cruel" sport as he attempts to salvage his season.

The 27-year-old German, champion for the last four years, heads into his home race this weekend sixth in the championship and without a win.

"It's been a tough start, a rough season so far," Vettel said.

"F1 can be fantastic, as I have experience of, but it can be very cruel in retiring from problems. You rely on your car. It is part of the game."

Mercedes are in a position to win every race if they want to, so it will be difficult to beat them

Sebastian Vettel

Vettel, who was speaking in an interview to be broadcast on BBC One during the highlights of the German Grand Prix on Sunday, has failed to finish three of the nine races so far this season as Red Bull have struggled for pace compared to the dominant Mercedes team.

He is 95 points - nearly four clear victories - behind championship leader Nico Rosberg of Mercedes and 28 points adrift of new team-mate Daniel Ricciardo, who has out-qualified Vettel five times since replacing fellow Australian Mark Webber.

Vettel has struggled to come to terms with the new F1 cars following rule changes this season but hopes things will turn around.

"I'm confident it will," he said. "I'm struggling to understand the car so we are testing a lot of things. Some work, some don't."

World Championship standings

After 2014 British Grand Prix (13 July)

Nico Rosberg

Mercedes

165

Lewis Hamilton

Mercedes

161

Daniel Ricciardo

Red Bull

98

Fernando Alonso

Ferrari

87

Valtteri Bottas

Williams

73

Sebastian Vettel

Red Bull

70

Vettel added that he was still enjoying F1, despite his problems.

He said: "I have one quote I very often read to myself, from a very good friend: 'Forget the people around you now; remember the little boy who was racing in go-karts, what you were dreaming of and what he wanted to achieve one day and what was his goal. Race for him.'

"I fell in love with the sport, I love racing. The amount of satisfaction I get just going around in a Formula 1 car makes me smile.

"If it is a bad day, then you tend to come out and say it's horrible and you don't enjoy it. But if you had to pick between that and doing nothing, you would always pick that."

Vettel says it would be premature to rule himself out of this year's title race

He insisted he has not given up hope of making up enough ground to win the championship over the remaining 10 races.

"If there is mathematically a chance, there is still a chance," he said.

"If things turn around from this weekend onwards, you'd be stupid not to take the opportunity. So you have to be optimistic.

"Being realistic, though, the gap is very big. Mercedes are in a position to win every race if they want to, so it will be difficult to beat them.

"We are not here to finish third or fifth. If that is the best you can do, you have to be happy with that and respect what other people are doing, but the goal is to win races and fight for the championship."

Watch Sebastian Vettel's interview during BBC Two's highlights of the German Grand Prix from 19:00 BST on Sunday.